A strong warm front associated with a low pressure system from the Gulf of Mexico caused a protracted precipitation event to occur in Pennsylvania. This was complicated by a very cold air mass that was in place over the state at the start. Some record breaking low temperatures occurred just the morning before. Snow overspread the region between 1 p.m. EST and 3 p.m. EST. The warm air had an easier time advancing aloft than near the ground as an unseasonably cold air mass was still in place. The snow changed to freezing rain about an hour after precipitation started around Philadelphia (4 p.m. EST). It took a bit longer elsewhere changing to freezing rain around 6 p.m. EST in the Philadelphia northwestern suburbs and Berks County, 7 p.m. EST in the Lehigh Valley and 8 p.m. EST in the Poconos north. Snowfall accumulations were an inch or less, except in the Poconos where up to three inches accumulated. Warmer air from the relatively warm Atlantic Ocean changed the freezing rain to plain rain around Philadelphia between 6 p.m. and 7 p.m. EST, but took until around 11 p.m. EST for the far Philadelphia northern suburbs and Berks County, around Midnight EST on the 16th in the Lehigh Valley and as late as 4 a.m. EST on the 16th in the Poconos. Before the change to plain rain occurred, around one quarter of an inch of ice accrued on exposed surfaces from the Poconos south into the northern Philadelphia suburbs.Travel on untreated roadways were treacherous. In Berks County, about 30 crashes were reported. Westbound Interstate 78 was closed in Greenwich Township because a tractor-trailer rolled onto its side. Sections of U.S. Route 422 were closed in Amity Township in both directions because of accidents. In the Lehigh Valley numerous accidents occurred as vehicles slid off roads, rolled over or skidded into each other. Other vehicles became stuck on the ice. Westbound Interstate 78 was closed near Hellertown (Northampton County). In Lower Saucon Township (Northampton County), four people were injured in a crash that blocked another section of Interstate 78 for three hours. A tractor-trailer was struck by two vehicles. Pennsylvania State Routes 191 and 512 were ice covered and vehicles were sliding off of Pennsylvania State Route 33. Carbon County in the Poconos also reported numerous crashes and many vehicles that slid off roads. Many schools were closed on the 16th in the Poconos and the Lehigh Valley. Even the Philadelphia Flyers were not immune from the effects of the ice as two separate multi-car crashes on the Walt Whitman Bridge closed the span for one hour. Two-thirds of the team was stuck in the traffic tie-up and the start of the game was delayed.Snowfall accumulations included 3.0 inches in Pocono Summit (Monore County), 2.6 inches in Lehighton (Carbon County) and 0.6 inches at the Lehigh Valley International Airport.The precipitation was caused by a low pressure system that developed on the Gulf Coast early on the 15th. A broad southerly brought moisture and much milder air into the region. The low itself moved northeast through the Delaware valley overnight on the 5th and was located near New York City at sunrise on the 16th. The track helped bring relatively warm air from the nearby Atlantic Ocean into the region and helped change the freezing rain to plain rain.

Winter Weather in DELAWARE, PENNSYLVANIA
From 15-DEC-05 15:00:00 to 15-DEC-05 19:00:00 (EST)
Reported by: AWOS,ASOS,MESONET,ETC

Winter Weather in PHILADELPHIA, PENNSYLVANIA
From 15-DEC-05 15:00:00 to 15-DEC-05 19:00:00 (EST)
Reported by: AWOS,ASOS,MESONET,ETC

Winter Storm in BERKS, PENNSYLVANIA
From 15-DEC-05 21:30:00 to 15-DEC-05 23:00:00 (EST)
Reported by: AWOS,ASOS,MESONET,ETC

Winter Storm in BUCKS, PENNSYLVANIA
From 15-DEC-05 22:00:00 to 15-DEC-05 23:00:00 (EST)
Reported by: AWOS,ASOS,MESONET,ETC

Winter Storm in CARBON, PENNSYLVANIA
From 16-DEC-05 00:00:00 to 16-DEC-05 04:00:00 (EST)
Reported by: AWOS,ASOS,MESONET,ETC

Winter Storm in CHESTER, PENNSYLVANIA
From 15-DEC-05 21:30:00 to 15-DEC-05 22:00:00 (EST)
Reported by: AWOS,ASOS,MESONET,ETC

Winter Storm in LEHIGH, PENNSYLVANIA
From 15-DEC-05 22:00:00 to 16-DEC-05 01:00:00 (EST)
Reported by: AWOS,ASOS,MESONET,ETC

Winter Storm in MONROE, PENNSYLVANIA
From 16-DEC-05 00:00:00 to 16-DEC-05 04:00:00 (EST)
Reported by: AWOS,ASOS,MESONET,ETC

Winter Storm in MONTGOMERY, PENNSYLVANIA
From 15-DEC-05 22:00:00 to 15-DEC-05 23:00:00 (EST)
Reported by: AWOS,ASOS,MESONET,ETC

Winter Storm in NORTHAMPTON, PENNSYLVANIA
From 15-DEC-05 22:00:00 to 16-DEC-05 01:00:00 (EST)
Reported by: AWOS,ASOS,MESONET,ETC